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Friday, 14 October 2011

Do Referees Subconsciously Influence Matches?

The Expected Points Model I use in this blog is a very potent weapon in analysis performance based questions in soccer.All things being equal the cumulative total pre game EP over a reasonably large number of games for individual teams almost always tallies up to be very close to the actual points a team achieves.If there is a major discrepancy between the actual and predicted points totals there is usually a readily discernible reason why.For example if we were to by pure chance select a series of games where the team was destined to have a player dismissed,the cumulative pre game EP for that team would be well above the actual points gained.However,the cause,namely the red cards would be readily apparent.

It is therefore possible to use an Expected Points approach to evaluate any influence a certain referee may
have had on the outcome of a batch of games.However,before I go any further I want to emphasis that because a referee shows up as an outlier in any analysis involving match decisions,it no way implies that there may be deliberate bias involved.People can respond subconsciously in different ways to very similar situations and if the majority react in a different way to you that difference can become apparent.It may present a problem in terms of consistency of decisions,but it doesn't automatically mean that there is deliberate bias at work.

Secondly,random events can converge to make a set of games appear unusual and the result of a common denominator such as the referee,when in fact they have just come about by random chance.I'll deal with these issues in a later post,but for now here's how games controlled by the major EPL ref's from the last seven seasons have panned out.

Recent and major decisions tend to be over emphasised in people's memories,so it's hardly surprising that every set of fans think that every official is out to get their team regardless of venue and regardless of their team's standing in the match in question.But it is an enduring opinion that refs favour either the home teams or the better teams in a game.This is reinforced because in general home sides and favourites will do more attacking,receive more free kicks and penalties and although this can be construed as favouritism from officialdom,it is really just down the better team getting it's just deserts.

These natural advantages enjoyed by home teams is already accounted for in the Expected Points calculation,so we can compare the cumulative pre game EP totals with the actual totals gained by the host and then sort them by referee to see if any patterns begin to emerge.All EPL games from the 2004-05 season until the present were included and any referee who officiated 30 games or less was excluded.The vast majority of the referees appear to officiate in games which on average produce actual cumulative points tallies that are extremely close to the pre game expectations.Mark Halsey for example officiated in 121 games and pre game estimates would have suggested that the home team would gain 198.5 points from those games.They actually gained 198 points.So from these figures we would have to conclude that Halsey was officiating in a way that corresponds very closely to the way officials have refereed in the past.Overall 13 of the 21 referees featured in the table saw their groups of matches produce home points that were within 4% or better of their expected value and the majority have been rewarded by being appointed to take charge of the FA Cup final.

Games officiated by Peter Walton saw the home side's actual points under perform the expected value by nearly 8% (two refs produced higher discrepancies,but their game tallies were each much less than Walton's total of 134 games).Again a caveat must apply.Firstly,these results could have arose through random chance or alternatively Walton may actually be one of the few officials who is able to resist the subconscious influence of the home support and it is his colleagues who are out of step.At the other end of the spectrum Mark Clattenburg is the ref with most games in the survey who saw an elevated points tally for the home teams he officiated.Home teams gained an average of 7% more points than expected when he was in charge.The most prestigious game either Clattenberg or Walton have taken charge of is the Community Shield.

Points accrued by home teams compared to pre game expectations sorted by referee.2005-11.

REFEREE.

PreGame Expected Points for Home Teams.

Actual Home Team Points.

% Difference.

Number of
Games.

L Mason.

145.3

157

8.0

86

M Clattenburg.

210.1

224

6.6

124

L Probert.

126.0

134

6.3

72

K Friend.

56.9

60

5.4

33

U Rennie.

81.3

83

2.1

50

C Foy.

247.4

251

1.4

145

P Dowd.

251.5

255

1.4

152

M Dean.

274.1

276

0.7

169

M Halsey.

198.5

198

-0.3

121

M Riley.

178.7

178

-0.4

118

M Atkinson.

256.4

254

-0.9

151

A Marriner.

177.6

175

-1.5

109

H Webb.

294.2

289

-1.8

177

A Wiley.

244.0

239

-2.1

145

R Styles.

186.3

180

-3.4

111

G Poll.

104.6

101

-3.5

61

S Bennett

231.4

222

-4.1

139

P Walton.

231.7

214

-7.6

134

M Jones.

109.0

100

-8.3

60

S Atwell.

69.8

62

-11.2

36

* denotes a cup final referee.

If we repeat the exercise by tracing the points haul for all pregame favourites a similar pattern appears.14 of the listed refs see their games come in at within 4% of the expected points total.Game favourites are not always readily identifiable,for example when a relegation candidate entertains a mid table team.So in the majority of these games there's not a huge amount of subliminal pressure to ensure that the "right" team wins.Games overseen by Phil Dowd have coincided with the likes of Arsenal,Chelsea and ManU failing to fulfil their pre game expectations,while Lee Probert controlled matches has seen the favourites overachieve.

Points accrued by match favourites compared to pre game expectations sorted by referee.2005-11

REFEREE.

Pre Game
Expected Points for Favourites.

Actual
Points won by Favourites.

% Difference.

Number of
Games.

L Probert.

133.2

149

11.8

72

A Wiley.

278.4

296

6.3

145

C Foy.

274.1

290

5.8

145

R Styles.

213.2

222

4.1

111

K Friend.

60.6

63

4.0

118

M Riley.

191.1

199

4.0

33

M Halsey.

226.1

234

3.5

121

S Bennett.

268.8

276

2.7

139

G Poll.

111.1

113

1.7

61

U Rennie.

93.7

95

1.4

50

M Clattenburg.

235.5

236

0.2

124

D Gallagher.

63.2

63

-0.3

34

P Walton.

259.8

256

-1.5

134

M Dean.

313.6

309

-1.5

169

M Atkinson.

279.1

272

-2.6

151

A Marriner.

212.0

205

-3.3

109

L Mason

163.2

157

-3.8

86

M Jones.

113.3

109

-3.8

60

H Webb.

324.8

310

-4.6

177

S Atwell.

69.5

62

-10.8

36

P Dowd.

287.7

255

-11.4

152

From the previous table is is evident that the interpretation and implementation of the laws in the EPL are very largely consistent with previous seasons.There are very few refereeing performances that deviate greatly from the expected outcome over a large enough batch of games.The fewer the games the more likely it is we will see batches of games that appear atypical and even where outlying officials have controlled large numbers of games the possibility for freak sequences to appear is real and present.

Poor or contentious decisions are often seen as the result of incompetence or malice,but more often they result from a subconscious desire by the officials to please the majority ( in the case of home field teams) or satisfy the consensus opinion (in the case of favourites).Managers often criticise officials often unjustly,but always to gain a possible advantage in future games where the previous,often well publicised vent will subconsciously "encourage"referees to favour their side to atone for previous mistakes.

Judging by the above results EPL referees are largely immune to such pressures or if they do allow their judgement to be swayed it is within the bounds of historical limits and therefore relatively consistent between referees.